A revealing new fight has erupted over the future of the inmate who admitted helping to kill a correctional officer at U.S. Penitentiary Atwater in California’s San Joaquin Valley.

On the eve of a Friday sentencing hearing, attorneys for mentally troubled inmate James Ninete Leon Guerrero are struggling to keep him out of the federal Supermax prison in Florence, Colo. Defense attorneys say Leon Guerrero’s mental frailties make him a bad match for the facility where severe conditions have prompted civil rights lawsuits.

“Mr. Leon Guerrero is not challenging the fact of his confinement, but rather the conditions of confinement,” Deputy Federal Public Defender Jonathan C. Aminoff wrote in a legal filing Sunday.

Prosecutors, though, say prison assignments are strictly up to the federal Bureau of Prisons. The ensuing conflict sheds light on broader questions about incarcerating the mentally ill.

In March, Leon Guerrero pleaded guilty to first-degree murder for helping to kill correctional officer Jose Rivera in June 2008. At the time, he was already serving a life sentence. Fellow inmate Joseph Cabrera Sablan still faces trial for the killing of Rivera. Prison videotape and witnesses identify Sablan as the one who stabbed Rivera multiple times, prosecutors say.

The plea agreement saved Leon Guerrero from a potential death sentence, but left unanswered the question of where he’d spend the rest of his life. Typically, inmates who kill while in prison are assigned to what’s formally called the U.S. Administrative Maximum Penitentiary at Florence.

The problem, Aminoff and fellow defense attorney Richard Novak say, is that Supermax is the worst possible place for Leon Guerrero. The remote facility currently houses more than 400 inmates, some of whom spend up to 24 hours a day in cells that measure 12 feet by seven feet.

“Many prisoners at ADX interminably wail, scream, and bang on the walls of their cells,” one lawsuit reported. “Some mutilate their bodies with razors, shards of glass, sharpened chicken bones, writing utensils, and whatever other objects they can obtain . . . others carry on delusional conversations with voices they hear in their heads, oblivious to reality.”

An inmate who joined a class-action lawsuit filed by the Washington Lawyers’ Committee for Civil Rights and Urban Affairs, former Florida resident and convicted bank robber John Jay Powers, amputated his “own fingers, testicle, scrotum and earlobes,” according to the lawsuit. Powers has since been transferred to a federal medical facility in Springfield, Mo., records show.

Denver-based U.S. District Judge Richard P. Matsch last year rejected Obama administration requests to dismiss the Supermax lawsuits. Appointed to the bench by President Richard Nixon, Matsch called one Supermax suit a “high priority case because of the public importance of it.”

The latest settlement negotiations were held May 15, court records show.

Since the lawsuits were filed, Bureau of Prison officials have opened a special 30-cell unit at U.S. Penitentiary Atlanta for inmates with serious mental illness. Officials also adopted a policy that inmates with “significant” mental health problems will only go to Supermax “if extraordinary security needs are identified that cannot be managed elsewhere.”

Into this mix steps Leon Guerrero, a 48-year-old Guam native who has spent much of his adult life in prison. Leon Guerrero, defense attorneys note in a recent filing, “has serious mental illnesses requiring psychiatric treatment, including psychotropic medication.” These conditions include bipolar disorder and an intellectual disability that defense attorneys had previously argued made him ineligible for the death penalty.

Medication has helped ease Leon Guerrero’s mental state, defense attorneys say. But if he’s placed at Supermax, they fear, he would no longer be medicated even as he’d face difficult conditions.

In court filings, defense attorneys asked U.S. District Judge Philip M. Pro to hold off on finalizing Leon Guerrero’s case until the Bureau of Prisons had assigned him to a prison other than the Supermax in Colorado. Federal prosecutors countered that prison assignments are up to the Bureau of Prisons and not individual trial judges.

“Moreover, the Supreme Court has made clear that an inmate has no right to be confined in any particular prison, nor does he have a right to be transferred to any particular prison,” Justice Department attorneys noted in a recent legal filing.